Myers' Psychology for the AP® Course, 4e, Unit 0, English

histogram

a bar graph depicting a frequency distribution.

operational definition

a carefully worded statement of the exact procedures (operations) used in a research study. For example, human intelligence may be operationally defined as what an intelligence test measures. (Also known as operationalization.)

standard deviation

a computed measure of how much scores vary around the mean score.

sampling bias

a flawed sampling process that produces an unrepresentative sample.

scatterplot

a graphed cluster of dots, each of which represents the values of two variables. The slope of the points suggests the direction of the relationship between the two variables. The amount of scatter suggests the strength of the correlation (little scatter indicates high correlation).

correlation

a measure of the extent to which two factors vary together, and thus of how well either factor predicts the other.

survey

a non-experimental technique for obtaining the self-reported attitudes or behaviors of a particular group, usually by questioning a representative, random sample of the group.

case study

a non-experimental technique in which one individual or group is studied in depth in the hope of revealing universal principles.

naturalistic observation

a non-experimental technique of observing and recording behavior in naturally occurring situations without trying to manipulate and control the situation.

skewed distribution

a representation of scores that lack symmetry around their average value.

experiment

a research method in which an investigator manipulates one or more factors (independent variables) to observe the effect on some behavior or mental process (the dependent variable). By random assignment of participants, the experimenter aims to control other relevant factors.

qualitative research

a research method that relies on in-depth, narrative data that are not translated into numbers.

quantitative research

a research method that relies on quantifiable, numerical data.

random sample

a sample that fairly represents a population because each member has an equal chance of inclusion.

correlation coefficient

a statistical index of the relationship between two variables (from −1.00 to +1.00).

meta-analysis

a statistical procedure for analyzing the results of multiple studies to reach an overall conclusion.

statistical significance

a statistical statement of how likely it is that a result (such as a difference between samples) occurred by chance, assuming there is no difference between the populations being studied.

normal curve

a symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean (about 68 percent fall within one standard deviation of it) and fewer and fewer scores lie near the extremes. (Also called a normal distribution.)

hypothesis

a testable prediction, often implied by a theory.

population

all those in a group being studied, from which random samples may be drawn. (Note: Except for national studies, this does not refer to a country’s whole population.)

double-blind procedure

an experimental procedure in which both the research participants and the research staff are ignorant (blind) about whether the research participants have received the treatment or a placebo. Commonly used in drug-evaluation studies.

single-blind procedure

an experimental procedure in which the research participants are ignorant (blind) about whether they have received the treatment or a placebo.

theory

an explanation using an integrated set of principles that organizes observations and predicts behaviors or events.

variable

anything that can vary and is feasible and ethical to measure.

random assignment

assigning participants to experimental and control groups by chance, thus minimizing preexisting differences between the different groups.

experimenter bias

bias caused when researchers may unintentionally influence results to confirm their own beliefs.

social desirability bias

bias from people's responding in ways they presume a researcher expects or wishes.

self-report bias

bias when people report their behavior inaccurately.

placebo effect [pluh-SEE-bo; Latin for“I shall please”]

experimental results caused by expectations alone; any effect on behavior caused by the administration of an inert substance or condition, which the recipient assumes is an active agent.

informed consent

giving potential participants enough information about a study to enable them to choose whether they wish to participate.

confounding variable

in an experiment, a factor other than the factor being studied that might influence a study’s results.

independent variable

in an experiment, the factor that is manipulated; the variable whose effect is being studied.

experimental group

in an experiment, the group exposed to the treatment — that is, to one version of the independent variable.

control group

in an experiment, the group not exposed to the treatment; contrasts with the experimental group and serves as a comparison for evaluating the effect of the treatment.

dependent variable

in an experiment, the outcome that is measured; the variable that may change when the independent variable is manipulated.

inferential statistics

numerical data that allow one to generalize — to infer from sample data the probability of something being true of a population.

descriptive statistics

numerical data used to measure and describe characteristics of groups; include measures of central tendency and measures of variation.

illusory correlation

perceiving a relationship where none exists, or perceiving a stronger-than-actual relationship.

replication

repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding can be reproduced.

peer reviewers

scientific experts who evaluate a research article’s theory, originality, and accuracy.

mean

the arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores.

range

the difference between the highest and lowest scores in a distribution.

validity

the extent to which a test or experiment measures or predicts what it is supposed to.

median

the middle score in a distribution; half the scores are above it and half are below it.

mode

the most frequently occurring score(s) in a distribution.

percentile rank

the percentage of scores that are lower than a given score.

falsifiable

the possibility that an idea, hypothesis, or theory can be disproven by observation or experiment.

debriefing

the postexperimental explanation of a study, including its purpose and any deceptions, to its participants.

effect size

the strength of the relationship between two variables. The larger the effect size, the more one variable can be explained by the other.

regression toward the mean

the tendency for extreme or unusual scores or events to fall back (regress) toward the average.

hindsight bias

the tendency to believe, after learning an outcome, that one would have foreseen it. (Also known as the I-knew-it-all-along phenomenon.)

critical thinking

thinking that does not automatically accept arguments and conclusions. Rather, it examines assumptions, appraises the source, discerns hidden biases, evaluates evidence, and assesses conclusions.